Because the French government tolerates intolerance, that's why.
The quintessential of globalism, cultural Marxism and internationalism is to tolerate everything, no matter how intolerant something can be.

Re: At least 12 killed and 10 injured in Muslim shooting attack at headquarters of Charlie Hebdo magazine in France

A lot of North Africans are accepted as French even by "French Racists" it seems. Southern France definitely has affinities with North Africa because of a long history of colonialism and migration of peoples.